The invention relates to the use of lasers in inspection systems or other sensing systems, particularly laser systems which can detect the three-dimensional position of a mechanical part in an assembly line. Such sensing systems require a laser projector to generate and direct a sensing beam and an image receiver to collect the beam reflected from the object being inspected or xe2x80x9csensedxe2x80x9d. There are well known devices (cameras) for collecting and processing the reflected beam, and apparatuses for focusing and directing the laser beam are available.
The present invention is directed to the laser driver for a laser sensing system. The laser driver is the portion of the sensing system which controls the generation of the laser beam. Currently, the preferred method of generating the laser beam is by use of a laser diode.
There were several problems in laser driver designs which existed prior to the present invention. A specific problem was the initial setting of the laser power, which had typically been accomplished through manual adjustment of a dial type potentiometer. A related problem has been accurate temperature control of the laser diode, as minor temperature changes will effect the wave length of the laser beam generated by the laser diode. It has been known to utilize an electric heater to maintain a minimum operating temperature, and it has been suggested that a TEC (thermoelectric cooler) could be utilized in connection with a laser driver for stabilizing the laser diode temperature which can be higher or lower than the ambient temperature. However, it is believed that, in spite of the need and suggestion, no cost effective apparatus has been designed to fit within the space confines provided for a laser driver, and particularly not in conjunction with the other features of the present invention.
Current laser sensing systems of the type described herein typically utilize a single laser beam due primarily to the cost and space constraints. The use of two laser beams greatly improves the sensing capabilities (resolution and accuracy) of the system, but has required two laser drivers or at least two separate PCBs (Printed Control Boards), one for each laser diode.
Laser diode technology is rapidly improving, and regularly produces more efficient, reliable, durable and powerful diodes. In current laser driver designs, the circuit is designed to handle one of two standard diode configurations, and will not accommodate the other configuration, thus eliminating from use a group of laser diodes which may have superior properties for a particular application.
An important concern in the laser sensing systems at issue is speed. Available laser drivers provide response times (turning the laser on to specification) in excess of 500 ms (xc2xd sec.). Improving response time provides additional time for the system to conduct the measurement or sensing operation and speeds up the entire sensing process.
A significant issue with respect to any laser based system is safety. However, current systems rely entirely upon a simple on-off circuit and do not monitor the condition of the laser diode. These systems cannot take advantage of the increased peak power available from a laser diode if the diode is pulsed rather than activated at a constant level (continuous waves).